With the development of DNA markers (also referred to as genetic markers or gene markers), both useful and undesirable traits can be rapidly and efficiently identified when improvement in plant varieties is intended. The development of DNA markers has advanced for a wide variety of practical plants as well as for model plants such as Arabidopsis thaliana and Oryza sativa. Thus, such markers significantly contribute to improvement in plant varieties.
Strawberries are known to be classified into one-season-bearing varieties and everbearing varieties. One-season-bearing varieties undergo floral bud formation under low-temperature and short-day conditions in autumn and flowering and fruiting in the following spring. Everbearing varieties naturally undergo floral bud differentiation under long-day and high-temperature conditions and thus undergo fruiting from summer to autumn in addition to spring. An example of a known variety of the latter is “Summerberry.” Since everbearing varieties are able to match demands in seasons when one-season-bearing varieties cannot be harvested, the development of improved everbearing varieties has been desired.
Sugimoto et al., 2005, Plant Breeding 124: 498-501 and Yamamoto et al., 2003. Kinki Chugoku Shikoku Agricultural Research 2: 42-44 describe that the F1 progeny generation resulting from the cross between an everbearing variety “Everberry” and a one-season-bearing variety “Toyonoka” was used to identify the RAPD marker associated with a gene associated with everbearing properties. However, the RAPD marker disclosed in Sugimoto et al., 2005, Plant Breeding 124: 498-501 and Yamamoto et al., 2003, Kinki Chugoku Shikoku Agricultural Research 2: 42-44 has drawbacks, such that the degree of linkage thereof to the gene associated with everbearing properties is low, the selection efficiency is poor, and it is thus not suitable for practical use.
JP 2006-42622 A discloses a DNA marker located in the vicinity of the gene associated with everbearing properties in strawberries, a primer used for amplifying such marker, and a method for distinguishing everbearing varieties from one-season-bearing varieties with the use of such marker in a simple manner. The DNA marker disclosed in JP 2006-42622 A is an ISSR marker, which is problematic in terms of convenience and accuracy in distinguishing. When the DNA marker disclosed in JP 2006-42622 A is amplified, for example, a plurality of bands appear from a single analyte. However, the target band is located in a position very close to other bands, and it is difficult to distinguish the target band from other bands. In addition, the degree of linkage thereof to phenotypes exhibiting everbearing properties is not strong, and the accuracy in selection is thus low.
In addition, Honjo et al., 2011, Breeding Research 13 (Additional Vol. 2): 265 discloses an SSR marker that is strongly linked to everbearing properties. The SSR marker disclosed in Honjo et al., 2011, Breeding Research 13 (Additional Vol. 2): 265 requires the use of an expensive electrophoresis apparatus with high accuracy for analysis, which could not be used conveniently for a simple test.